Taiwan Semiconductor Manufacturing Comp. Ltd.

Der-Chen Chen

Yi-Huang Wu

An FET semiconductor substrate includes source/drain regions with an outer buried contact region overlapping the drain region, a gate oxide layer, and a polysilicon layer over the gate oxide layer. An inner buried contact opening through the polysilicon and the gate oxide layer reaches down to the substrate over the outer buried contact region. An inner buried contact region, within the outer buried contact region, is self-aligned with the buried contact opening. A second polysilicon layer formed over the gate oxide layer reaches down through the buried contact opening into contact with the inner buried contact region. An interconnect and a gate electrode are formed from the polysilicon layers. Source/drain regions are self-aligned with the gate electrode and whereas the drain region is spaced from the inner buried contact region, the outer buried contact region interconnects the drain region with the inner buried contact region.

Outer buried contact region connecting drain region to inner buried

A method of forming an FET device starts by forming a sacrificial layer over a semiconductor substrate and an outer buried contact region is produced by ion implantation into the substrate, followed by stripping the sacrificial layer, forming a gate oxide layer, and depositing polysilicon over the gate oxide layer. Then, etch an inner buried contact opening through the polysilicon and the gate oxide layer down to the substrate over the outer buried contact region forming an etched buried contact opening. Implant dopant into the substrate through the inner buried contact opening in the second mask to dope the substrate forming the inner buried contact region within the outer buried contact region self-aligned with the etched buried contact opening. Form a blanket, second polysilicon layer over the gate oxide layer reaching down through the etched buried contact opening into electrical and mechanical contact with the inner buried contact region. Etch to form the interconnect and the gate electrode from the polysilicon layers, and form source/drain regions.

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Hsin-Chu, Taiwan

Der-Chen Chen